Other Operating Costs (Benefit) (Components of Other Operating Costs (Benefit)) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Income And Expenses [Abstract]
Adjustments to office closure obligations, discounted and net of expected sublease income	$ 141	$ 509	$ 1,354
Rent expense during office consolidation			1,247
Accelerated depreciation	101	33	165
Contingent acquisition liability adjustments, net	2,213	1,330	(13,047)
Loss on disposition of assets			283
Deferred debt issuance costs write off	145
Other impairment			98
Other costs	1,620
Other operating costs (benefit)	$ 4,220	$ 1,872	$ (9,900)